In communication systems, signal generators such as transmitters and receivers commonly employ filters to remove noise in the signal path. The systems typically employ static filters that are designed to remove noise in specified frequency ranges. For example, noise in a transmitter may include spurious noise frequencies (also referred to as spurs) resulting from component mismatches and signal leaks, as well as harmonic noise due to mixing the intermediate frequency signal with the reference frequency signal. The noise signal may vary for different signal bands. Therefore, the frequency range that should be filtered is often variable. A static filter is usually unable to eliminate the harmonic noise frequencies that falls within the filter's bandwidth. It would be desirable to have a technique that could reduce variable frequency noise. It would also be desirable if the circuitry could be implemented without significantly increasing the complexity of the existing systems.